An ecological niche can be defined as the functional role an organism performs in the ecosystem in order to sustain it's life. It includes how an organism obtain it's food, which type of food it consumes, what type of habitat is used by the organism, interaction of the organism with the other organism of the ecosystem.
A niche is a part of an organism habitat as the habitat is responsible for the functional role performed by the organism. For example, how an organism compete with other organism of the same or different species to obtain the habitat.
